1. Field of the Invention
The present invention relates to the field of modern electronic audio/video home entertainment systems. More particularly, the present invention relates to the field of speaker arrangements for stereo surround sound audio systems.
2. Description of the Prior Art
Modern electronic audio/video home entertainment systems have become very popular today. Many people desire to have complete audio/video systems installed at their own homes to make so called "home theaters" for enjoying individualized entertainment.
Referring to FIG. 1, there is shown a typical set up of a "home theater" entertainment system for user 10. The system includes a television (TV) set 12 and an audio/video components rack 14. The TV 12 may be a big screen or projection TV. The audio/video components rack 14 may comprise various audio/video components. One critical component is a receiver 16 which serves as the control center of all the audio and video components of the entire audio/video system. The audio components of the rack 14 may include a compact disc (CD) player, cassette tape recorder/player, digital audio tape (DAT) recorder/player, and turntable. The video components of the rack 14 may include video cassette recorder (VCR) and laser disc (LD) player.
The home theater system further comprises a speaker system, including a right front speaker 22, a left front speaker 24 and two rear speakers 26, all connected to receiver 16 by wires 28. The term "speaker" used throughout this application does not refer to a single loudspeaker, but rather a unit of loudspeakers. A "speaker" used in this sense typically comprises three basic parts. The first part includes one or more loudspeaker drivers, such as a "tweeter" which reproduces high frequency sounds, a "midrange" which reproduces mid-frequency sounds, and a "subwoofer" which reproduces low frequency sounds. The second part includes a crossover network which divides the input frequencies into two or more bands for their appropriate drivers. The third part is an acoustic cabinet which houses the loudspeaker drivers.
Therefore, in this application the term "speaker" refers to the independent cabinet in which one or more drivers and crossover networks are installed. The term "driver" then refers to the single push-pull loudspeaker driver such as a tweeter, a midrange, a full-range, a woofer and a subwoofer.
Right front speaker 22 shown in FIG. 1 is a typical example of a traditional "3-way" speaker. It has a rectangular box shaped cabinet 30. Three drivers are mounted inside the cabinet 30. The three drivers are: tweeter 32, midrange 34 and subwoofer 36. The physical dimensions of the drivers are often measured by the diameters of their respective diaphragms. For a home stereo system, the size of the tweeter 32 may be between 1/2 and 2 inches, the size of the midrange 34 may be between 31/2 and 6 inches, and the size of the subwoofer may be between 6 and 10 inches. The right front speaker 22 also includes a crossover network which is usually located on the back side of the speaker and has two terminals for accommodating wires 28.
Early home stereo systems reproduce stereo sound effect through two separate channels: a right front channel and a left front channel. The advanced home stereo systems now typically reproduce surround sound effect in four separate channels. Two more channels are provided in addition to the right and left front channels, including a rear surround channel and a center channel. The rear surround channel is used primarily for time-delay surround effect, and the center channel is used primarily for on-screen dialogue. Almost all CDs, LDs and DAT music tapes, most VCR movie tapes and audio cassette music tapes, and many TV and radio programs broadcast on network or cable systems are now encoded with all four channels.
In the systems shown in FIG. 1, right front speaker 22 is connected to the right front channel of receiver 16, left front speaker 24 is connected to the left front channel of receiver 16, and the two rear speakers 26 are connected to the rear surround channel of the receiver 16. The speaker built into TV 12 may be used as a center channel speaker and connected to the center channel of receiver 16, if input terminals are provided on TV 12. Otherwise a separate speaker may be used as the center channel speaker (not shown).
There are two common problems in most of the conventional home entertainment systems. The first common problem is that the conventional home entertainment systems usually has no separate center channel speaker. Additional center channel speakers become more desirable because they produce much clearer sound effect for dialogue, and deliver more realistic sound effects because the sound is coming from the center, where the TV is placed and where the sound of dialogue is supposed to come from. Separate center channel speakers also become more desirable because the speakers built into TVs usually produce less effective sound effects than separate speakers. Some receivers in conventional home entertainment systems have a so-called "phantom" mode to solve the problem of having no center speaker. In such "phantom" mode the signal of the center channel is sent to the two front speakers. The two front speakers then reproduce synthesized sound for the non-existing center channel speaker. However, the quality of the synthesized "phantom" sound produced by the front speakers cannot be as good as the quality of the real sound produced by a real center channel speaker.
The second common problem is that in most of the conventional home entertainment systems, each front speaker is a large cabinet housing directional and non-directional drivers. The tweeter and midrange drivers are directional drivers which require careful placement of the front speakers so their sound can be properly delivered to the user. On the other hand, the subwoofers are non-directional drivers and may be placed at any location. Because the front speakers include directional drivers, they have to be placed in certain locations. However, their large physical dimensions often make it hard to arrange the speaker with existing furniture. The placement of the speakers are often awkward and alter the arrangement and appearance of the user's living room dramatically. Some home entertainment systems have utilized a so-called "satellite" speaker system to solve the placement problem. In such satellite speaker system the directional and non-directional drivers in each of the front speakers are separated and installed in a separate cabinet. The smaller-sized directional drivers, including tweeter and midrange, are installed in a small cabinet. The larger-sized non-directional driver, the subwoofer, is installed in a large cabinet. The small cabinets of the directional drivers are the "satellite" of the speaker system. Since they are smaller, it is much easier to place them according to the set up and location of the user's listening area. The large subwoofer cabinets, on the other hand, do not have to be placed at a certain location and may even be placed behind furniture. However, having many separate speaker cabinets undoubtedly increases the complexity of installation and maintenance of the speaker system.
Therefore, it will be desirable to provide surround sound stereo audio systems for people's home theater entertainment systems, which not only provide additional and separate center channel speakers, but also provide effective as well as efficient arrangement of the speakers.